Electrochemical assessment of the protective properties for alkyd paint films with various thickness

Abstract

The aim of this paper was to investigate the influence of the film thickness on the anticorrosive properties of alkyd films. The films were realized in three thickness ranges (20-25, 40-45 and 60-65 mu m) on carbon steel substrate. The electrochemical measurements (anodic polarisation and electrochemical impedance spectroscopy - EIS) were used for assessment of the protective properties of alkyd films in acid, neutral and basic solutions at 25 degrees C temperature during a 5000 h period. Porosity, water and ions permeability, adhesion to metallic substrate and efficiency of the films were determined. The experimental results showed that the increase of the film thickness determines the decrease of the dissolution current density of the carbon steel substrate under organic film and moves the corrosion potential in electropositive direction. The interpretation of the impedance spectra (Nyquist and Bode diagrams) with the immitance analysis Equivcrt. Program permitted modelling of the carbon steel/alkyd film interface with electrical equivalent circuits.